Duplicating system



United States Patent 3,415,186 DUPLICATING SYSTEM Fred A. Fend, Pittsford, N.Y., assignor to Xerox Cor oration, Rochester, N.Y., a corporation of New York No Drawing. Filed Feb. 10, 1966, Ser. No. 526,362 5 Qlaims. (Cl. 101-468) This invention relates in general to imaging systems and, more particularly, to improved pressure transfer masters, their manufacture and use.

Various techniques have been developed for making multiple copies by the transfer of a relatively dry imaging material or dry ink. One well known dry transfer technique is the production of carbon copies in a typewriter. This technique suifers serious deficiencies in certain areas. For example, extremely light weight copy paper must be employed in order to properly transmit pressure through at least two or three copies. Because the pressure of the type character is not uniformly transmitted throughout the entire thickness of the sandwich formed by the carbon sheets and copy papers, the legibility of those carbon copies more remote from the type characters drops off markedly. Since the ink on the carbon paper must transfer readily under the application of pressure, it also tends to smudge and spread on the copy sheets, thereby producing fuzzy, illegible and non-permanent images. The ink on the surface of the carbon paper itself is easily smudged and often soils the hands and clothing of the operator. Additionally, it is very laborious and time-consuming to correct errors on carbon copies because each copy must be individually corrected. Many copying machines are available for producing multiple copies of printed and other intelligence by conventional processes such as xerography, photocopying, thermo and diazo processes. However, each of these processes require complex and expensive apparatus. Less expensive duplicating processes such as spirit-duplicating processes and stencil-duplicating processes are deficient for several reasons. In both of these processes, the liquid coloring material employed often soils the hands and clothes of the operator. The image sharpness of copies made by stencil or spirit duplicating processes is very poor. This loss of sharpness in the case of spirit-duplicating is due to a slight bleeding of a dye caused by the solvent. In the case of stencil-duplicating, bleeding occurs in the stencil due to the characteristics of the stencil material which must be so constructed as to permit passage of ink in the character areas. Although some of these techniques produce multiple copies which are superior to carbon copies, the copies produced are somewhat more expensive than carbon copies for short runs.

When duplicate copies are required in a number of remote locations, the copies may be produced at each separate location or produced at a central location and subsequently distributed to the remote locations. Production of copies at each remote site requires the placement of expensive and space-consuming duplicating or copying machines at each remote location. When copies are produced at a central location, and sent to each remote site, both shipping costs and storage space requirements increase significantly. Further, where consumption of duplicate copies at each remote site is variable and unpredictable, under-production or over-production may occur at the centralized duplicating site. Over-production of duplicates at the central location is undesirable because the cost of materials and shipping are unnecessarily high and valuable storage space at the remote site is occupied by useless duplicates. In countries where paper is very expensive, particularly in some of the under-developed countries, neither of the alternative methods described above are satisfactory because of the often prohibitive 3,415,186 Patented Dec. 10, 1968 costs involved. The foregoing problem is of particular importance to large institutions such as the school systems in some of the Latin American countries. It would appear that a system which would permit production of stable inexpensive duplicating masters at a central location and subsequent production of copies with the master at remote sites would solve some of the above-described problems, particularly if high quality copy production could be accomplished at the remote site with inexpensive apparatus.

Relatively simple duplicating systems have been proposed in US. Patent 3,122,094 and German Patent 646,530 which should permit duplication without the aid of complex and expensive equipment. In these systems, a Wax or parafiin treated transfer sheet is pressed against a surface carrying colored material to pick up a portion of the colored material and subsequently pressed against a copy sheet to transfer thereto a portion of the coloring material which is picked up in the preceding pressure transfer step. Pressure transfer duplicating techniques of this type have not been employed commercially because in the present state of the art they are not capable of producing a sufiicient number of high resolution and high density copies as to make them commercially attractive to the user as a replacement for carbon paper or other duplicating techniques. Apparently, no coloring material has been found which satisfactorily possesses the many critical properties required for this type of process. The coloring material must possess good transfer properties under the high rates of shear applied during the initial transfer step so that sharp clear images are produced on the transfer sheet which will not spread or smudge to any appreciable extent. This requirement is difficult to satisfy because a heavy coating of coloring material must be transferred during the initial transfer step to provide an adequate quantity of coloring material on the transfer sheet for subsequent production of multiple copies. Further, the transferred coloring material must be capable of being retransferred under relatively lower rates of shear to form high density copies which do not smudge or retransfer upon subsequent handling. If too much coloring material is re-transferred from the transfer sheet to the copy sheet, the supply of coloring material remaining on the transfer sheet will be so rapidly depleted that few copies will be produced with the transfer sheet. On the other hand, if the quantity of coloring material retransferred from the transfer sheet is meager, the density and legibility of the copy images Will be poor. Further, multiple copy transfer sheets employing conventional inks possess very poor shelf life. The reduced shelf life may be due to many factors. One factor may be the loss of usable ink through migration of ink components into the surface of the master. Another factor may be ink oxidation. A further factor may be evaporation of ink components. The problems inherent in the foregoing processes are enormous when one considers the smudging and image density problems encountered with ordinary carbon paper in which coloring materials are transferred only once.

It is therefore, anobject of this invention to provide a duplicating system overcoming the above noted deficiencies.

It is another object of this invention to provide a duplicating system which permits the employment of inexpensive, compact and simple duplicating devices.

It is another object of this invention to provide a duplicating system which permits efiicient utilization of copy paper.

It is another object of this invention to provide a novel pressure transfer duplicating master capable of producing short run multiple copies inexpensively.

It is another object of this invention to provide a dupli- 1O eating master having physical and chemical properties superior to those of known duplicating masters.

The above objects and others are accomplished generally speaking, by providing a duplicating system which employs a master comprising a substrate carrying on at least one surface thereof, a fixed image comprising encapsulated ink. Duplicate copies are produced by placing the master in faceto-face contact with a copy sheet and pressing the two together to rupture the ink capsule and release a portion of the ink. Upon separation of the copy sheet, from the master sheet, a portion of the ink remains on the master for use in making additional copies. Although it is not clear, it is believed that when the fixed capsule images are crushed during the copy making process, the capsule Walls form a 3-dimensional sponge-like skeleton which promotes regulation of the quantity of ink released by the master to each successive copy sheet to provide both high density images and a large number of copies. Regulation of ink transfer is also aided by employment of specially formulated inks and proper capsule deposition techniques.

Any suitable conventional process may be employed to encapsulate the ink of this invention. Typical encapsulation techniques include dip coating, phase separation from solvent solutions, fluidized bed coating and centrifugal casting. Solid ink particles may be dip coated by immersing the particles in a. liquid coating material and then hardening or drying the coating material on the surface of the particles. The liquid coating material may comprise a molten material or a solution of the coating material. In the phase separation technique, a macro-molecular wall material is dissolved in a solvent and a solvent insoluble liquid or solid ink is dispersed in the resulting solution. The solubility characteristics of the solvent is then changed to cause the wall material to come back out of solution. As the wall material separates from solution, it collects around and encapsulates the dispersed ink particles. The wall material may comprise a water-soluble polymer such as gelatin, gum arabic, or starch. After the ink core particles have been dispersed in the solvent, separation is initiated by removing part of the solvent, adding more wall material, adding other soluble material or cooling the mixture. The wall is solidified by drying, polymerizing, tanning or other suitable techniques depending on the specific wall material employed. Suitable capsule wall and solvent materials and methods of encapsulating dispersed core material are disclosed by Green et al. in US. Patent 2,800,457. Solid core materials, immiscible liquids or mixtures of the foregoing may be employed in phase separation encapsulation processes. In the fluidized bed coating technique, dry ink particles are suspended on a relatively strong upwardly flowing current of heated air into which a solution of Wall material is atomized. The wall material deposits on the dry ink particles and the solvent evaporates. Once the capsule wall is built up to the desired thickness, the introduction of coating solution is terminated. The flow of heated air is maintained until the particles are dried. In the centrifugal casting technique, a membrane of fiuid wall material is formed across an orifice and a tiny droplet or particle of ink is projected through the orifice to allow the wall material to envelop the droplet or particle. After the wall material envelops the ink particle, it is hardened by solvent extraction, chemical reaction, solvent evaporation or cooling, depending upon the specific wall material employed. A

l typical centrifugal capsulating method is disclosed by Somerville, Jr. in US. Patent 3,015,128. The capsule size produced by any of the foregoing techniques is necessarily related to the sharpness of definition desired in the ulti- 5 mate image.

Any suitable coating process may be employed to deposit the encapsulated ink particles in image configuration on the master sheets. Typical deposition processes include electrostatic, letterpress, gravure, and lithographic deposition processes. Vthere conventional printing techniques such as letterpress, gravure or lithographic printing are employed to deposit the ink, the printing pressure must be carefully regulated to avoid premature rupturing of the encapsulated ink. Optimum results are obtained when the encapsulated ink is deposited by electrostatic methods.

Since no printing pressure is used when the capsules of this invention are eleetrostatically deposited, the problem of prematurely rupturing the capsules during deposition is eliminated. One well known method of electrostatically depositing particles is disclosed by C. F. Carlson in US. Patent 2,297,691. This method involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing the layer to a light and shadow image to dissipate the charge on the areas of the layer exposed to the light and developing the resulting latent electrostatic image by depositing on the image a finely divided electroscopic material referred to in the art as toner. The toner will normally be attracted to those areas of the layer which retain a charge, thereby forming a toner image corre- 3O spending to the latent electrostatic image. This powder may then be fixed to the photoconductive insulating layer or transferred to a receiving surface such as paper. The transferred image may subsequently be permanently affixed to the receiving surface as by heat. Instead of latent image formation by uniformly charging the photoconductivc layer and then exposing the layer to a light and shadow image, one may form the latent image by directly charging the layer in image configuration, Several methods are known for applying the eleetroscopic particles to the latent electrostatic image to be developed. These methods include cascade development, magnetic brush development, powder cloud development and liquid development as described in US. Patents 2,6122,- 552; 2,874,063; 2,221,776; and 2,891,911 respectively.

If the encapsulated particles are employed in cascade or magnetic brush development processes, the particles should have a diameter less than about microns and preferably less than about 30 microns for optimum ease of handling and highest image quality. For powder cloud 50 and liquid development methods, the particles may have a still smaller size, preferably less than about 10 microns in diameter. However, it is apparent that the particle size chosen is necessarily related to the sharpness of definition desired in the ultimate copy image.

When electrostatic imaging is employed to form the master of this invention, it is preferred that the encapsulated ink possess humidity insensitive properties. Humidity sensitive capsule walls such as the gelatin capsule wall described in US. Patent 2,800,458 are often unsatisfactory for electrostatic imaging because t. eir triboelectric properties fluctuate with changes in the humidity in the atmosphere. Humidity insensitivity may be imparted to preencapsulated material, such as inks coated with gelatin, by overcoating the capsule With a hydrophobic (35 material. As a preferred procedure, the hydrophillic capsule material is dipped or immersed into a solution of a mixture of polystyrene and polystyrene homologues dissolved in toluene, xylene, or a similar non-aqueous organic solvent. The mixture is suitably agitated and dried by spray drying or the like to produce capsules substantially uniformly coated with the polystyrene resin. Any other suitable colored or colorless hydrohobic resin may be employed in place of polystyrene. Typical hydrophobic resins include: acrylic resins, methacrylic resins, polystyrene, polyethylene, polypropylene, modified phenolformaldehyde resins and mixtures thereof. Suitable methods of coating hydrophillic capsules are described by C. I. Claus in U.S. Patent 3,080,318.

In a preferred procedure for electrostatically producing an imaged master of this invention, the ink particles coated with a hydrophobic coating is mixed with a granular bead-like carrier material such as those disclosed by Walkup in US. Patent 2,618,551, generally in the amount of about 1 part by weight of the coated dry ink and about 99 parts by weight of the carrier composition. The mixed developer material may then be employed to develop electrostatic images by cascading the developer mixture across the surface of a plate bearing the electrostatic image. The developed image may be fixed to the plate or electrostatically transferred to a sheet.

Since the novel masters of this invention must be stable and durable during storage and handling, the deposited encapsulated ink must be suitably fixed to the surface of the master sheet. When conventional xerographic over coating, solvent or heat fixing methods are employed to fix the encapsulated dry ink to the surface of the master sheet, the resulting product is usually unsatisfactory for use as a master. For example, when a film-forming material is applied over the deposited images to fix the deposited images to the surface of the master sheet, the film-forming material often interferes with the subsequent transfer of the ink to a cop-y sheet. When heat fusion is employed to fix the images to the master sheet, the heat often causes the capsule walls to melt and flow toward the master surface. This migration of the capsule Walls toward the master is undesirable because the ink cores are often exposed to the atmosphere thus defeating the purpose of encapsulating the ink. Further, the heat required to properly fix the capsules often causes the ink to flow laterally thus resulting in distorted images. Several fixing methods have been found which adequately fix the capsules to the surface of the master sheet Without detrimentally affecting capsule integrity or interfering with ink transfer. When the capsules comprise an inner hydrophillic wall and an outer hydrophobic wall, the capsules may be fixed to the surface of the master sheet by solvent fixing methods. However, the solvent selected must be capable of dissolving the outer capsule Wall but not the inner capsule wall. For example, when the dry ink 1s coated with an inner coating of gelatin and an outer coating of polystyrene resin, a solvent such as toluene or xylene which dissolves polystyrene but does not dissolve gelatin should be employed. The solvent causes the polystyrene capsule wall material to flow from the inner gelatin cansule toward the master surface. Some of the dissolved polystyrene capsule wall material penetrates the interstices of the master sheet surface and binds the gelatin capsule to the master sheet. The dissolved outer capsule wall also binds adjacent capsules together. ObVlously, any solvent, organic or inorganic, Which will dissolve the outer capsule wall but not the inner wall may be employed. Heat fixing may be used to fix encapsulated ink particles to the surface of the master sheet if the capsule wall comprises a thermoplastic material. When the capsule wall comprises a thermoplastic resin, the surface of the master sheet may be precoated with a solid solvent or plasticizer for the thermoplastic wall material. The solid solvent or plasticizer should effectuate complete thermoplastic resin fusion under heating conditions at which the thermoplastic resin per se affords only marginal or no fusion. Any suitable solid plasticizer or solvent may be employed. Typical solid plasticizers and solvents include ethylene glycol dibenzoate, dimethyl isophthalate, N-cyclohexyl -toluene sulfonamide, N-ethyl p-toluene sulfonamide, triphenyl phosphate, glycerol tribenzoate, dicyclohexyl phthalate, diphenyl phthalate, acetanilide, o-chloroacetoacetanilide, p-dibromobenzene, rn-nitroaniline, 4-nitrobiphenyl and mixtures thereof. The solid plasticizer or solvent may be applied to the master surface by any conventional method such as spraying,

dipping, fluidized bed coating, brushing or roll coating. The solid plasticizer or solvent may be applied alone or in combination with other materials as a powder, disper- S1011, solution, vapor, emulsion, or melt. Optimum results have been obtained when the solid plasticizer or solvent is applied and mixed with a binder because the problem of dust contamination is eliminated. Any suitable binder may be employed to immovably attach the solid plasticizer or solvent to the master surface. Typical binders include: acetylated starch, styrene-butadiene latex, carboxymethyl cellulose, polyvinyl pyrrolidone, and mixtures thereof. Surprisingly, electrostatically deposited images formed on master surfaces treated with a binder and a solid plasticizer are more optically dense than toner images formed on untreated master surfaces. Additionally, paper master sheets treated with a binder and plasticizer mixture lie flatter after toner fusion than untreated paper masters. It is preferred that the binder content remain below about 20%, based on the weight of the plasticizer or solid solvent as this provides much more efficient fusing apparently because more plasticizer is available at the surface where the capsule is to be fused to the master. Surface coatings containing at least about /2 pound of solid solvent per 1300 square feet are satisfactory. When the solid plasticizer or solvent material is incorporated into the master sheet, e.g., by impregnation, proportionately more plasticizer or solvent is necessary in order to maintain a sufiicient quantity of plasticizer or solvent at the surface of the master sheet. Clearly, the solid plasticizer or solvent treated master surface should be used with those capsules having walls which will be plasticized or dissolved by the specific solid plasticizer or solvent employed on the master surface. Selection of compatible combinations of solid plasticizer or solvent and thermoplastic resin capsule wall materials will be obvious to those skilled in the art. Blends of two or more plasticizers or solvents may be used to broaden the thermoplastic resin spectrum of the master surface. After deposition of the image on the master surface, the imaged master is preferably heated from the image-free side to insure that the thermoplastic resin wall material at the interface between the capsule and the master sheet surface is melted. Backside heating reduces the possibility of melting the entire capsule wall of the exposed capsules. Heat may, however, be applied from the imaged side because the capsule wall material adjacent to the treated master surface will fuse at lower temperatures. Alternatively, the surface of the master sheet may be pre-treated with a thermoadhesive material which upon heating becomes sufiiciently tacky to bind the deposited encapsulated dry ink particles to the surface of the master sheet. When thermoadhesive coatings are employed on the master sheet, the capsule wall need not be constructed of low melting point thermoplastic material. Any suitable thermoadhesive material may be employed to bind the capsules of this invention to the master surface. For example, thermoplastic resins such as cellulose acetate, cellulose nitrate, polystyrene, methacrylic resins and mixtures thereof may be employed as a thermoadhesive material. If desired, the imaged master may be produced by first depositing a tacky settable adhesive material in image configuration and then applying loose encapsulated ink particles to the adhesive image. The adhesive may thereafter he set by drying or curing; The excess capsules which do not adhere to the deposited adhesive material are removed prior or subsequent to setting by any suitable means such as a current of air.

When multiple layers of capsules are deposited, the uppermost layers may be fixed by heat applied from the imaged side of the sheet. However, heat energy must be applied with a relatively high degree of care to effect capsule sintering while simultaneously maintaining capsule wall integrity. Dual walled capsules having a high melting point inner wall and a low melting outer wall are less vulnerable to Wall destruction during heat fixing.

Solvent fixing of multiple layers is preferred because the capsules may be joined to the master surface and to other capsules at each point of contact with less danger of destroying the capsule walls. Multiple layers of dual wall capsules of the type described above may be solvent-fixed without fear of harming the inner solvent-insoluble capsule wall. Obviously, the foregoing fixing techniques may also be employed to fix ink capsules deposited on the master sheets by any of the non-xerographie methods mentioned above.

Any suitable ink having reserve transfer capabilities may be used in the capsule cores of this invention. Inks having reserve transfer properties are capable of forming a plurality of images from one master image. Thus, when ink from an ink master image is transferred to a copy sheet to form a duplicate copy, a portion of the ink in the ink master remains available in reserve on the master for additional copies. Fair results are obtained with viscous liquid inks. However, the copies obtained are few in number and tend to bleed and offset. The copy images are fuzzy and lack good image density. A typical liquid ink composition may be formulated as follows:

Ingredient: Parts by weight Nigrosene black 8 Pigments 6 Diglycol laurate 14 Tri-cresyl phosphate 15 Quality images are obtained with capsule cores comprising pasty or dry solid inks. Typical solid resin-base inks may be formulated as follows:

Ingredient: Parts by weight Adhesive resin 8-14 Mineral oil -35 Carbon black 5-15 Typical solid wax-base inks may be formulated as follows:

Ingredient: Parts by weight Microcrystalline wax 5-10 Pigment 60-80 Modifier 5-10 In the immediately preceding formulation, the pigment may comprise conventional pigments such as iron oxide or carbon and the modifier may comprise petrolatum or chlorinated rubber. For more uniform ink transfer, good image density and better resolution, the following polysiloxane-base dry ink capsule core formulation is very satisfactory:

Ingredient: Parts by weight Pigment 33-72 Wax soluble dyes 2-10 Waxes 3-11 Adhesive resin 3-10 Polysiloxane -50 Although good results are obtained using the general formulation above, from 10-20 copies can be made with the preferred and optimum formulations set forth below.

A small amount of wax soluble or wax dispersible dye is employed in the dry polysiloxane-base ink formulation above to improve ink uniformity. The dyes are intimately deployed throughout the ink and eliminate the possibility of undesirable clear wax particles appearing in the final copy. To avoid undesirable coloring and bleeding, the quantity of Waxoline Blue and Waxoline Black (Imperial Chemical Industries Ltd.) should not deviate from; that indicated in the formulations above. Any suitable dye, in lieu of or in addition to the Waxoline dyes mentioned above may be employed in the ink formulation. Typical wax soluble dyes include: Victoria Blue (C H N HCI), Methyl Violet (methylrosaniline chloride), Nigrosine Base NBC and mixtures thereof.

A combination of waxes, a silicone such as dimethyl polysiloxane gum and adhesive resin provides a vehicle or binder with the desired rheological properties for the dry polysiloxane-base ink formulation. The waxes, resin and silicone form an incompatible but uniform and homogeneous mixture that permits partial transfer under low rates of shear.

The employment of a hard microcrystalline wax plasticized by beeswax is preferred because optimum transfer properties are achieved. However, other suitable waxes may be substituted for the microcrystalline wax and beeswax in the polysiloxane-base ink formulations above. Typical waxes include: paraffin, polyethylene wax mixtures, candelilla wax, hard microcrystalline wax mixed with plasticizers and mixtures thereof.

The silicone gum employed in the dry polysiloxane-base ink formulations above comprises a clear viscous dimethylpolysiloxane gum having a plasticity number from about to about 120, as measured with the Williams plasticity number test, ASTM, D/926, at room temperature for 3 minutes. The incompatibility between the silicone gum and the other materials in the binder such as the waxes and resin is a key factor in achieving the desired rheological properties mentioned above. Any highly viscous liquid or waxy polysiloxane having a viscosity greater than about 30,000 centistokes may be employed. Typical polysiloxanes include the dimethyl, methyl vinyl, methylphenyl, ethyl, polysiloxanes and mixtures thereof.

The inclusion of an adhesive resin reduces smudging by improving the overall cohesion of the ink formulation. Any suitable adhesive resin may be used. Typical adhesive resins, preferably of low molecular weight, include: polystyrene, styrene-butadiene, vinyl chloride-vinyl acetate copolymer, polyvinylacetate, polyterpenes, chlorinated rubber, tall oil rosin and mixtures thereof.

Excellent images having high density and greater smudge resistance are obtained when inks containing two or more different pigments such as those in the formulations above are employed. It has been found that maximum density and high smudge resistance are obtained when the ratios of various pigments of different sizes are adjusted to provide maximum packing density. Excess pigment results in lower resolution and increased smudging. On the other hand, image density suffers when the quantity of pigment is insufficient. Any suitable pigment material may be employed depending upon the effect and color desired. Typical pigments include: carbon black, black and red iron oxide of the magnetic and non-magnetic types, chromium oxide, chrome yellow, chrome green, toluidine red toner, phthalocyanine, molybdates and iron blues, zinc powder, bronze, aluminum powder and mixtures thereof. Fillers such as barium sulfate and graphite flour are also considered pigments for the purposes of this disclosure.

The dry polysiloxane-base ink described above is produced in the following manner. First, silicone gum is dissolved in xylene. The dyes are then melted together with the waxes and resin by heating the mixture to about 250 F. for approximately 20 minutes. Next, a solution of silicone gum is added to the melted mass and ground in a ball mill for about 1 hour. The dry pigments are mixed in a roller mill for about 1 hour and the resulting mixture is added to the foregoing mixture and milled until the pigment is well wetted. By first dissolving the silicone gum and then adding it to the molten waxes, dyes and resin it is possible to maintain a workable mixture of incompatible materials. Also, by delaying the wetting of the pigment materials and adding the finest pigments first, the possibility of grinding these materials to too fine and uniform a size is minimized.

The following examples further define, describe, and compare exemplary methods of preparing and using the masters of the present invention. Parts and percentages are by weight unless otherwise indicated.

In the following, Examples I-VIII are carried out with dry ink particles coated with an inner gelatin coating prepared by the method disclosed by Green et al. in US. Patent 2,800,457 and an outer capsule wall prepared by solution coating followed by spray drying as described by C. J. Claus in U.S. 3,080,318. The treated zinc oxide master sheets in Examples I-IV carry a surface coating of a plasticizer mixture applied by means of a smooth metal reverse roll in a Dietzco-Dixon Pilot Coater followed by doctoring with a reverse rotating number 4 wirewound rod. The images in Examples I-IV are formed directly on a paper backed photoconductor of Zinc oxide in an insulating melamine formaldehyde resin as described in US. Patent 3,080,251.

Example I An encapsulated ink is prepared and xerographically deposited in image configuration onto a plasticizer treated paper sheet. The ink contains the following ingredients:

Ingredients: Parts by weight Iron oxide (IRN 350) 26.0 Carbon black (Peerless Beads) 21.0 Coal fines (Austin Black) .0 Waxoline blue GA 5.0 Waxoline black BA 5.0 Microcrystalline wax 5.0 Beeswax, white 2.0 Polystyrene (Piccolastic A-S) 8.0

Dimethyl polysiloxane gurn (General Electric silicone gum SE 76) 30.0

After xerographically depositing the encapsulated ink onto a zinc oxide sheet treated with 150 parts ethylene glycol dibenzoate, two parts polyvinyl pyrrolidone (PVP Type K-30), the capsule image is fixed to the sheet by heating the image-free side of the imaged sheet with a bar type heater. The imaged and fixed master is then placed face down on a copy sheet and passed between two pressure rollers. This last step is repeated with new copy sheets and the resulting copies examined.

Twelve copies having good legibility and high density are obtained.

Example II The method and materials of Example I are repeated except that three high viscosity dimethyl polysiloxane oils (viscosities 30,000, 60,000 and 100,000 centistokes) are substituted for the silicone gum. Twelve copies of good legibility and density are obtained.

Example III The method and materials of Example I are repeated, but the silicone gum ingredient is omitted. Only 1 to 2 copies are produced.

Example IV The procedure and materials of Example I are repeated except that the following ink composition is substituted for the ink composition employed in Example I.

Ingredients: Parts by weight Beeswax 4.0 Polystyrene 8.0 Microcrystalline wax 11.0 Carbon black 50.0 Coal fines 10.0 Waxoline Blue GA 8.0 Waxoline Black BA 7.0

Eight fairly legible copies are produced.

Example V An encapsulated ink is prepared and xerographically deposited in image configuration onto a paper sheet. The ink contains the following ingredients:

Ingredients: Parts by weight Iron oxide (IRN 350) 26.0 Carbon black (Peerless Beads) 21.0 Coal fines (Austin Black) 5.0 Waxoline Blue GA 5.0 Waxoline Black BA 5.0 Microcrystalline wax 5.0 White beeswax 2.0 Polystyrene 8.0 Dimethyl polysiloxane (General Electric Silicone Gum SE 76) 30.0

After the capsules are xerogr-aphically deposited on an electrostatic image-bearing plate, the resulting capsule image is electrostatically transferred to a paper sheet. The transferred image is then fixed to the sheet by exposing the imaged sheet to xylene vapors and thereafter slowly heating the treated sheet to remove the deposited xylene. The images and fixed master is then placed face down on a copy sheet and passed between two pressure rollers. This last step is repeated with additional copy sheets and the resulting copies examined. Fourteen copies having good legibility and relatively high density are obtained.

Example VI A method and materials of Example V are repeated except that three high-viscosity dimethyl polysiloxane oils (viscosities 30,000, 60,000 and 100,000 centistokes) are substituted for the silicone gum. Fourteen copies of good legibility and density are obtained.

Example VII The method and materials of Example V are repeated but the silicone gum ingredient is omitted. Only 1 to 2 copies are produced.

Example VIII An encapsulated dry ink is prepared and xerogr-aphically deposited in image configuration onto a plasticizer treated paper sheet. The ink core contains the following ingredients:

The dry ink core is surrounded by a coating comprising 9 parts copolymer of styrene and n-butyl methacrylate, one part carbon black, and one part polyvinyl .butyral. After the capsules are xerographically deposited on an electrostatic image-bearing plate, the resulting capsule image is electrostatically transferred to a paper sheet treated with one-hundred fifty parts dicyclohexyl phthalate, one part sodium salt of processed rosin (Dresinate X) and four parts styrene-butadiene latex (Dow 636). The transferred capsule image is then fixed to the sheet by heating the image-free side of the imaged sheet with a bar type heater and the imaged side with an infrared lamp. The imaged and fixed master is then placed face down on a copy sheet and passed between two pressure rollers. This last step is repeated with new copy sheets and the resulting copies examined. Fourteen copies 11 having good legibility and relatively high density are obtained.

Example IX The procedure and materials of Example VIII are repeated except that a thermoadhesive coating of low molecular weight (7000) polyethylene (Bakelite DYGT) was substituted for the plasticizer treatment material. Twelve copies having good legibility and relatively high density are obtained.

Although specific materials and conditions are set forth in the foregoing examples, these are merely intended as illustrations of the present invention. Various other suitable ink cores, wall materials, copy sheet material, plasticizers, binders, solvents, thermoadhesives, deposition processes and fixing processes such as those listed above may be substituted for those in the examples With similar results. Other materials may also be added to the ink core, capsule wall, plasticizer or binder to sensitize, synergize or otherwise improve the storage and duplieating properties or other desirable properties of the system.

Other modifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.

What is claimed is:

I. A pressure transfer duplicating master comprising a base member and a profusion of pressure rupturable capsules fixed to a surface of said base member in image configuration, said rupturable capsules comprising an outer capsule Wall material and a homogenous inner ink Core comprising from about 33 to about 72 parts by weight of pigment dispersed in a binder, said binder comprising from about 3 to about 11 parts by weight of wax, from about 3 to about parts by weight of an adhesive resin and from about to about 50 parts by weight polysiloxane having a viscosity greater than about 30,000 centistokes and which is incompatible with said wax and said adhesive resin.

2. A method of preparing a pressure transfer duplicating master comprising providing a base member having an image receiving surface thereon, providing pressure rupturable capsules comprising an outer capsule wall terial and a homogenous inner ink core comprising from about 33 to about 72 parts by weight of pigment dispersed in a binder, said binder comprising from about 3 to about 11 parts by weight of wax, from about 3 to about 10 parts of an adhesive resin and from about 25 to about 50 parts by weight of a high molecular weight polysiloxane having a viscosity greater than about 30,000 eentistokes and which is incompatible With said wax and said adhesive resin; forming an image of said rupturable capsules on said image receiving surface; and fixing said image of rupturable capsules to said image receiving surface.

3. A duplicating method comprising:

(a) providing a pressure transfer duplicating master having a base member and a profusion of pressure rupturable capsules attached to a surface of said base member in image configuration, said rupturable capsules comprising an outer capsule wall material and a homogeneous inner ink core comprising from about 33 to about 72 parts by weight of a pigment dispersed in a binder, said binder comprising from a out 3 to about 11 parts by weight of wax, from about 3 to about 10 parts by weight of an adhesive resin and from about 25 to parts by weight of a high molecular Weight polysiloxane having a viscosity greater than about 30,000 centistokes and which is incompatible with said wax and said adhesive resins;

(b) positioning a copy sheet against said rupturable capsules and said surface of said base member;

(c) applying pressure to said master and said copy sheet to express said ink from said rupturable capsules into engagement with said copy sheet; and

(d) removing said copy sheet from said master whereby a portion of said ink is transferred from said surface of said base member to said copy sheet in accordance with said image configuration.

4. The method of claim 3 wherein said ink core further contains about 2 to about 10 parts by weight of a dye which is soluble in said Wax component of said binder.

5. The method of claim 3 wherein steps (b), (e) and (d) are repeated with additional copy sheets to produce a plurality of copies from said master.

References Cited UNITED STATES PATENTS 2,297,691 10/1942 Carlson. 2,866,711 12/1958 Hart 10631 2,939,009 5/1960 Tien 11736.1 2,953,470 10/1960 Green et al. 2,971,916 2/1961 Schleicher et al. 3,001,873 9/1961 Foris 10l-149.4 3,016,308 1/1962 Macaulay. 3,036,924 5/1962 Newman 1l736.l

DAVID KLEIN, Primary Examiner.

US. Cl. X.R. 101473 

3. A DUPLICATING METHOD COMPRISING: (A) PROVIDING A PRESSURE TRANSFER DUPLICATING MASTER HAVING A BASE MEMBER AND A PROFUSION OF PRESSURE RUPTURABLE CAPSULES ATTACHED TO A SURFACE OF SAID BASE MEMBER IN IMAGE CONFIGURATION, SAID RUPTURABLE CAPSULES COMPRISING AN OUTER CAPSULE WALL MATERIAL AND A HOMOGENEOUS INNER INK CORE COMPRISING FROM ABOUT 33 TO ABOUT 72 PARTS BY WEIGHT OF A PIGMENT DISPERSED IN A BINDER, SAID BINDER COMPRISING FROM ABOUT 3 TO ABOUT 11 PARTS BY WEIGHT OF WAX, FROM ABOUT 3 TO ABOUT 10 PARTS BY WEIGHT OF AN ADHESIVE RESIN AND FROM ABOUT 25 TO 50 PARTS BY WEIGHT OF A HIGH MOLECULAR WEIGHT POLYSILOXANE HAVING A VISCOSITY GREATER THAN ABOUT 30,000 CENTISTOKES AND WHICH IS INCOMPATIBLE WITH SAID WAX AND SAID ADHESIVE RESINS; (B) POSITIONING A COPY SHEET AGAINST SAID RUPTURABLE CAPSULES AND SAID SURFACE OF SAID BASE MEMBER; (C) APPLYING PRESSURE TO SAID MASTER AND SAID COPY SHEET TO EXPRESS SAID INK FROM SAID RUPTURABLE CAPSULES INTO ENGAGEMENT WITH SAID COPY SHEET; AND (D) REMOVING SAID COPY SHET FROM SAID MASTER WHEREBY A PORTION OF SAID INK IS TRANSFERRED FROM SAID SURFACE OF SAID BASE MEMBER TO SAID COPY SHEET IN ACCORDANCE WITH SAID IMAGE CONFIGURATION.
 5. THE METHOD OF CLAIM 3 WHEREIN STEPS (B), (C) AND (D) ARE REPEATED WITH ADDITIONAL COPY SHEETS TO PRODUCE A PLURALITY OF COPIES FROM SAID MASTER. 